Half-Life

Radioactive Half-life

The time it takes for the number of nuclei of a radioactive element to halve or the time it takes for the count-rate of radioactive radiation to halve.

Random Decay Nature

Radioactive decay is random in nature meaning it is not possible to predict when a specific individual atom will decay.

Decay Curves

Graphs of count-rate against time used to determine the half-life of a radioactive substance.

Count-rate

The measure of the number of decays per unit time from a radioactive source.

Uranium - 235 Half-life

704 million years.

Plutonium - 239 Half-life

24,110 years.

Carbon - 14 Half-life

5,730 years.

Technetium - 99m Half-life

6 hours.

Polonium - 218 Half-life

3 minutes.

Measuring Thickness

Beams of beta radiation can be used to monitor thickness of materials like aluminium foil or paper.

Sterilisation

Gamma radiation can be used to kill microbes and sterilise medical equipment.

Smoke Alarms

Alpha radiation is used in smoke alarms to ionise the air allowing an electrical current to flow.

Medical Tracers

Radioactive materials used inside the body to help image organs or monitor fluid flows.

Technetium-99m

A gamma source with a half-life of 6 hours used for medical imaging.

Cancer Treatment

Gamma radiation directed towards cancerous cells to kill them and prevent spreading.

Targeted Alpha Therapy (TAT)

A treatment using alpha radiation injected directly into a tumor to kill cancerous cells.

Carbon Dating

Using radioactive carbon-14 to date organic ancient artefacts based on its decay.

Carbon-14 Decay

Living plants and animals absorb carbon-14 when alive, stopping when they die, allowing for dating based on decay.

Example of Carbon-14 Dating

If an old bone has 25% of the carbon-14 of a living bone, it is 11,460 years old.